1. Field of the Invention
The invention relates to a wheelchair for invalids, and particularly for individuals having a permanent handicap, which utilizes battery driven, combustion driven, hydraulically driven or generator driven motors for effecting the driving of the main wheels of the wheelchair and the steering thereof.
2. Summary of the Prior Art
Power operated wheelchairs have long been known in the prior art. The vast majority of previously issued patents, however, disclosed power operated wheelchairs wherein a separate driving motor was provided for each of the two driving wheels of the wheelchair.
As is well known to wheelchair occupants, whenever a conventional power operated wheelchair, having two power driven wheels and two castering wheels for steering, is driven along the side of a slope, the wheelchair will always tend to turn from a desired direction relative to the slope due to the tendency of the castering wheels to turn downwardly regardless of whether the castering wheels are forwardly or rearwardly located relative to the power driven wheels. The maintenance of steering in a desired direction becomes a difficult task, particularly to seriously handicapped individuals who may have to resort to the use of finger operated electrical switches, or in severe cases, to switches operated by movements of the head. Another difficulty with the conventional powered wheelchair lies in the fact that such wheelchairs generally have the power wheels mounted rearwardly of the center of gravity of the wheelchair when the occupant is sitting in the wheelchair. If, by inadvertence, full forward power is supplied to the driving wheels, or when climbing a steep slope, there is a definite tendency for the wheelchair to tilt backwardly, and in many cases to overturn, due to the location of the center of gravity of the wheelchair assemblage and occupant just forward and well above the power driven wheels.
Wheelchairs are also known to have power driven wheels located forwardly of the center of gravity of the wheelchair and castering or steerable wheels are provided rearwardly of the center of gravity. These wheelchairs are extremely difficult to steer due to the fact that the non steerable wheels will only find directional equilibrium when trailing the center of gravity. Manufacturers of this type of wheelchair have resorted to power steering of the castering wheels with limitations normally imposed with this system.
It is therefore obvious that improvements are sorely needed in the art of power driven, steerable wheelchairs in order to overcome each of the aforementioned disadvantages of the prior art wheelchair designs.